Multi-electrode glow discharge tubes



y 1, 1963 D. REANEY 3,090,893

MULTI-ELECTRODE GLOW DISCHARGE TUBES Filed March 7, 1961 4 Sheets-Sheet 1 1r, 5 F .1. g 2? 27 0044440 REAA/E) ATTOk/VE J May 21,

F'iled March 7, 1961 1963 D. REAN EY MULTI-ELECTRODE GLOW DISCHARGE TUBES 4 Sheets-Sheet 2 y 1953 D. REANEY 3,090,893

MULTI-ELECTRODE GLOW DISCHARGE TUBES l3 l4 4 Sheets-Sheet 3 Filed March 7, 1961 Fig .4. 36

United States Patent 3,099,893 MULTI-ELECTRODE GLOW DISCHARGE TUBE Donald Reaney, Long Eaton, England, assignor to Ericsson Telephones Limited, London, Engiand, a British company Filed Mar. 7, 1961, Ser. No. 94,020 Claims priority, application Great Britain May 16, 1960 11 Claims. (Cl. 315135) The present invention relates to multi-electrode glow discharge tubes of the type comprising a common electrode and a ring of electrodes adjacent the common electrode in a gas-filled envelope, the ring of electrodes being made up of a sequence of main electrodes and guide electrodes and the arrangement being such that a glow discharge may be struck between any main electrode and the common electrode and a discharge thus struck may be moved from main electrode to main electrode by way of intervening guide electrodes by the application of operating pulses to the guide electrodes. Such tubes are hereinafter referred to as of the type specified. The invention also relates to circuits incorporating such tubes.

Common examples of tubes of the type specified are selector tubes. The common electrode is almost invariably an anode and the other electrodes cathodes. A selector tube may comprise a number (say of main cathodes connected to independent valve pins. Two guide electrodes are interposed between each pair of main cathodes. The guide electrodes fall into two classes, namely first guide electrode and second guide electrodes. Proceeding round the ring of cathodes the following recurring sequence obtains:

Main cathode, first guide electrode, second guide electrode, main cathode The first guide electrodes are connected in common to one valve pin and the second guide electrodes to another valve pin. In operation a discharge is struck between one main cathode and the common anode. This discharge can be moved round from main cathode to main cathode to any selected main cathode by the application of pulses to the first and second guide electrodes. Hence the name selector tube. Output signals indicative of the position of the glow discharge can be derived from load impedances connected to the main cathodes. Such signals are used for a variety of purposes including that of simply showing which main cathode is invested with the discharge. Such uses sometimes cause a heavy discharge current to be passed in the selector tube which lessens the life of a tube. A particular example will be considered hereinafter.

It is an object of the invention to provide a tube of the type specified which is more versatile in respect of its capabilities for providing output signals than are known tubes and which is, in particular, readily susceptible of being designed to feed or control devices drawing relatively high current.

A tube of the type specified according to the present invention is characterised in that at least one main electrode has associated therewith an auxiliary electrode disposed in that region between the main electrode and the common electrode which is, in operation, occupied by a glow discharge struck between the main electrode and the common electrode. The or each main electrode having an associated auxiliary electrode can be disposed somewhat further away from the common electrode than the guide electrodes and other main cathodes, if any, and the or each auxiliary electrode can be disposed on the direct line from its associated main electrode to the common electrode at the same distance from the common electrode as the guide electrodes. Alternatively the main and guide electrodes can lie conventionally in one ring with the or each auxiliary electrode nearer in to the common electrode Sfihdfi Fatented May 21, 1963 in the direct line between its associated main electrode and the common electrode.

It can be seen that an auxiliary electrode is subjected to a switching eiiect. Thus when a discharge is struck between the associated main electrode and the common electrode a ready current path exists between the auxiliary electrode and the main electrode and between the auxiliary electrode and the common electrode. No such current path exists when there is no discharge between the main electrode and the common electrode. Which of the two paths mentioned current flows in when a discharge is present will depend upon the external circuit. If the auxiliary electrode is left floating it will assume a positive potential when the discharge is present because of the collection of positive ions. If the auxiliary electrode is raised above this potential it will function as an auxiliary anode and current will flow from it to its associated main electrode (assuming the main electrodes to be cathodes and the common electrode to be an anode as is almost always the case with tubes of the type specified). The main charge carriers in this current are positive ions flowing into the main cathode.

It will be convenient to point out here that one of the most important factors controlling tube life when the common electrode is an anode is disintegration of the main electrodes (cathodes) by ionic bombardment. Attempts to draw heavy discharge currents increase such bombardment and reduce tube life. The provision of an auxiliary electrode operated as an anode in conjunction with its associated main cathode does not in itself lead to an increase in tube life as the current flowing into the main cathode is not decreased. The surface area of the main cathode can be increased however so that the current per unit area of electrode is maintained at a level which does not result in undue cathode disintegration.

It is also possible to operate the auxiliary electrode as a cathode by reducing its potential below the positive potential assumed if the electrode is left floating.

If a tube according to the invention is a selector tube it will, unless designed for a special purpose, have an auxiliary electrode associated with every main electrode. The switching efiect on these auxiliary electrodes caused by the discharge which is moved round the selector tube can be used for a variety of output and control purposes. One usage in which the auxiliary electrodes function as anodes connected to the cathodes of a register tube, whereby that cathode of the register tube connected t the auxiliary electrode associated with the selector to! main electrode invested with a glow is invested with glow will subsequently be described.

Throughout this specification register tube means multi-cathode glow discharge tube in which the cathodes are shaped to the outline of diflerent symbols. When a discharge is struck between an anode and one cathode, a symbol is displayed by virtue of the glow with which the cathode is invested.

Another known example of a tube of the type specified is a counter tube. In such a tube most (usually all but one) of the main electrodes are connected together. An output is taken only from the separate main electrode or electrodes. Each time an output signal is obtained it indicates that a certa n number of pulsing operations, moving the discharge from main electrode to main electrode, have been performed. Such tubes commonly have a total of ten main electrodes and are used as decade counters.

It Will be seen that a tube according to the invention can be used as a counter tube. Only one main electrode may have an associated auxiliary electrode, for example. Every time the discharge reaches this mean electrode the switching effect on the auxiliary electrode indicates a certain count. The signal produced in a circuit connected to the auxiliary electrode may be regarded as a carry signal,

that is a signal indicating carry one to a counter representing the next higher order of magnitude when a plurality of counters are connected in cascade. Counting may be additive or subtractive. and the carry signal may indicate either a positive or a negative carry. Known measures, such as the use of routing guides (guide electrodes taken out to separate connections) can be used to difierentiate between positive and negative carry when the tube is used bi-directionally.

It will be appreciated that the distinction between a selector tube and a counter tube need not lie in any constructional differences in the tubes, but in the manner in which the tubes are used. Thus a tube in which every main electrode has an associated auxiliary electrode may be used as a counter tube simply by making use of a selected one or ones of the auxiliary electrodes to obtain carry signals. It will also be apparent that, if output signals are to be derived solely from one or more auxiliary electrodes, it is immaterial as to whether the main electrodes are independent or connected.

In general therefore the invention resides broadly in the provision of one or more auxiliary electrodes as aforesaid and not in the particular use to which the tube is put or the particular circuit connected to the tube. It will be apparent from the foregoing that the uses of the tube can be many and varied.

The invention will now be further described by way of example with reference to the accompanying drawings in which:

FIG. 1 is an elevation of a tube embodying the invention,

FIG. 2 is a section on the line IIII in FIG. 1, and

FIG. 3 is a circuit diagram showing a tube as shown in FIG. 1 used in conjunction with a register tube,

FIG. 4 illustrates the construction of a second embodiment of the invention,

FIG. 5 is a plan view of a ceramic spacer used in the second embodiment,

FIG. 6 is a section on the line 6-6 in FIG. 5,

FIG. 7is a plan view of another ceramic spacer,

FIG. 8 is a section on the line 88 in FIG. 7, and

FIG. 9 is a diagram of an alternative circuit to that shown in FIG. 3.

The tube shown in FIGS. 1 and 2 has an evacuated envelope 10 including a base 11 in the form of a thick disc of glass through which pass a plurality of valve pins 12. The pins lie on two concentric circles and most terminate conventionally some little distance above the disc or base 11. Three pins 13 in the inner circle however extend right to the top of the electrode structure within the tube and support a disc-like anode 14. Thus upturned tabs (not shown) on the disc 14 are welded to flattened top ends of the pins 13.

Three ceramic spacing sleeves 15 fit over the pins 13 respectively and rest against the base 11. A stack of discs is sandwiched between the sleeves 15 and three further ceramic spacing sleeves 16 extending between the top of the stack and the anode 14. The discs in the said stack will be listed from the bottom upwards:

(a) A mica disc 17 of diameter little less than that of the envelope 10 (internally) and having ears 18 which press against the envelope, thus centring and giving rigidity 'to the structure supported by the pins 13.

(b) A ceramic disc 19.

(c) 'A metal disc 20 (of purpose to be described).

(d) A mica disc 21.

(e) A metal disc 22 similar to the disc 20 and insulated from it by the mica disc 21.

(f) A ceramic disc 23.

(g) A mica disc 24 similar to the disc 17, and

(h) A ceramic disc 25.

The anode 14 is surrounded by forty rod-like electrodes extending parallel to the axis of the tube up to the level of the anode as indicated at 26 in FIG. 1. As may be best seen in FIG. 2, thirty of the electrodes are equidistantly spaced round one circle concentric with the anode. These thirty electrodes consist of ten auxiliary electrodes A1 to A10, ten first guide electrodes G1 and ten second guide electrodes G2. The sequence followed is Al, G1, G2, A2, G1, G2, A3 A10, G1, G2, A1.

The ten auxiliary electrodes are connected to individual ones of the pins 12. The ten first guide electrodes G1 are connected together and to one of the pins 12. Thus all electrodes G1 are welded to ears on the metal disc 22, one electrode G1 continuing right down to one of the pins. The ten second guide electrodes G2 are similarly connected together and to one of the pins 12 by Way of the metal disc 20.

As will be apparent from FIG. 1 the guide electrodes pass through holes in the disc 24 and are thus properly positioned and aligned. The auxiliary electrodes pass through holes in both the disc 24 and the disc 17. So also do the ten remaining electrodes surrounding the anode which consists of ten main cathodes K1 to K10 lying on a ring concentric with the first-mentioned ring but of larger radius. Each of these main cathodes is connected to an individual one of the pins '12 and is covered with an insulating ceramic sleeve 27 in the region lyingbetween the discs 17 and 24. As can be seen in FIG. 2 the cathode K1 is radially in line with the auxiliary electrode Al, the cathode K2 is radially in line with the auxiliary electrode A2 and so on. The main cathodes are all of larger diameter wire than the auxiliary and guide electrodes.

In describing the operation of the tube it will be convenient initially to ignore the auxiliary electrodes A1 to A10. Thus, in FIG. 3, the tube is represented conventionally at ST. The anode is connected to +475 volts through a resistor RS and the cathodes K1 to K10 are connected to earth through individual resistors R1 to R10. Assume that a discharge is struck between K1 and the anode. When the guide electrodes G1 and G2 are pulsed in well known manner the discharge moves to K2 and on subsequent pulsings successively to K3, K4 and so on. The fact that the cathodes K1 to K10 are further away from the anode 14 than are the guide electrodes has been found not to affect theoperation of the tube. Moreover, though it is preferred to adopt the positioning shown and described, whereby each main cathode is equidistant from the guide electrodes to either side of it, it has been found that satisfactory operation can be obtained when the cathodes are displaced in the circumferential direction to some extent. i

If the auxiliary electrodes are left floating, their presence has no eifect on the ordinary operation of the tube,

though when the cathode K1 for instance is invested with a glow, thepotential of the auxiliary electrode A1 rises by reason of ion collection to a value of the order of volts. The main cathode passes about 1 milliamp as is usual.

FIG. 3 shows how a register tube RT can be controlled by the selector tube ST, making use of the auxiliary electrodes. Before describing what is shown it should be pointed out that, if an attempt is made to control the register tube from the ordinary main cathodes a discharge current appreciably in excess of 1 milliamp is drawn and the tube life is shortened. It will be appreciated that a register tube requires more current than a selector tube on account of the relatively large area of a cathode of a register tube. The main cathodes K1 to K10 of the present tube are thicker than the guide electrodes G1 and G2 and the auxiliary electrodes A1 to A10.

The register tube RT has ten cathodes in the shape of the numerals l, 2, 3 9, 0. These are connected to the auxiliary electrodes A1 to A10 respectively and through respective resistors R11 to R20 to a common, floating terminal TT the anode of the register tube is connected through a resistor RR (47 KS2) in series with a switch S to the 475 volt supply.

The switch S is normally open and the selector tube ST performs whatever selecting function is allocated thereto in perfectly normal manner. When, from time to time, it is desired to see which of the main cathodes K1 to K is the selected cathode at that time (the cathode invested with a glow) the switch S is closed.

When the switch S is open all the cathodes of the register tube RT assume the same potential by virtue of their connection to the common terminal TT through the resistors R11 to R which are each of 82 KS2.

Assume that, when the switch S is closed, the discharge in the selector tube is on the cathode K1. Current can therefore flow readily from the auxiliary electrode A1 to the cathode K1 (the auxiliary electrode A1 functioning as an anode). Accordingly a discharge strikes in the register tube RT between the anode and the cathode 1 which is thereby illuminated. The current path from +475 volts to earth is through the switch S, resistor RR and the discharge in the tube RT to the cathode 1, thence to the auxiliary electrode A1 and through the discharge in :the tube ST to the main cathode K1 and through the resistor R1 to earth.

If, while the switch S is still closed, the guide electrodes G1 and G2 are pulsed to move the discharge in tube ST to the main cathode K2, the discharge in the tube RT to cathode 1 extinguishes and a discharge to cathode 2 strikes. The 475 volt potential cannot maintain the first discharge when the ready current path from A1 to K1 does not exist.

Whilst the switch S is closed the register tube RT draws about 2.5 milliamps and this current is passed by the appropriate main cathode of the selector tube. The main cathodes are however of sufi'iciently thick wire to pass this current without undue disintegration from ion bombardment.

It will be understood that other external circuit connections may be made in which the auxiliary electrodes function as cathodes rather than anodes.

In FIG. 4 the main cathodes and guide electrodes have been omitted for clarity but the circle on which they lie is indicated by a line 30. The auxiliary electrodes are similarly indicated by a line 31 and as is indicated by this line, the auxiliary electrodes are cranked.

The common anode 14 is supported by a single, central rod 13 which continues down through the valve base to form the central valve pin. Stacked on this rod are a sleeve 15, a small ceramic disc 32 and a fiat metal annulus 33 to which all but one of ten main cathodes are connected. The tenth cathode is taken to a separate pin and the tube is therefore suitable for decade counting applications. On top of the metal annulus 33 is another small ceramic disc 34, a flat metal annulus 35 to which all the ten second guide electrodes are connected, a third small ceramic disc 36, a flat metal annulus 37 to which all the ten first guide electrodes are connected, a mica centralizing disc 38, a large ceramic disc 39 and a sleeve 16.

All three small discs 32, 34 and 36 are identical and are illustrated in FIGS. 5 and 6. Each disc is pierced by a central bore 40 for the anode support rod 13 and by ten bores 41 in a ring round the bore 40. The portions 31a (FIG. 4) of the auxiliary anodes ascending from their respective valve pins and forming leads to the electrodes proper pass through these bores. The upper surface of each disc has a very slightly raised central platform 42 which centres the metal annulus stacked on top of the ceramic disc, as indicated at 33 in FIG. 6. The platform 42 is formed with a central depression 43. A boss 44 is provided on the lower surface of each disc and the boss 44 of the upper discs 36 and 34 respectively fit into the depression 43 of the discs 34 and 32 respectively. This arrangement provides good insulation between the anode rod 13 and the connecting annuli 33, 35 and 37.

The large ceramic disc 39 (FIGS. 7 and 8) has a boss 45 on its lower surface which fits into the depression 43 in the disc 36. A central bore 46 is provided for the rod 13 and ten surrounding bores 47 line up with the bores 41 in FIG. 6. At the upper surface of the disc 39 the bores 47 terminate in slots 48 directed radially outwardly. The radial limbs of the auxiliary electrodes 31 indicated at 31b in FIG. 4 lie in these slots. The efiective portions 310 of the auxiliary electrodes stand up from the radially outer ends of the slots 48.

The disc 39 has finally a surrounding ring of thirty bores for the main cathodes (bore 49) for the first guides (bores 50), and for the second guides (bores 51). All these bores are counterbored as indicated at 52 to increase the lengths of leakage paths. The bores 49 are radially aligned with the slots 48 and are of larger diameter than the bores 47, 50 and 51. This is because the main cathodes are of larger diameter wire than the guides and auxiliary electrodes in order to allow for increased cathode currents.

In this tube it will be seen therefore that the main cathodes and guides lie in one ring and the auxiliary electrodes are in an inner ring, each between its associated main cathode and the common anode.

FIG. 9 shows an alternative circuit for driving a register tube RT from a tube embodying the invention. The essential difference from the circuit shown in FIG. 3 is that the terminal TI is not floating but is returned to the positive supply terminal at 475 volts through a resistor R21.

In the first instance this assists the initial striking of the tube by placing the auxiliary anodes A1 to A10 at the full supply voltage. But for this the auxiliary anodes have a marked screening et'r'ect tending to prevent ready striking.

Secondly this arrangement ensures that the non-glowing cathodes of the register tube RT are held at a sufliciently high potential for no glow to form thereon. Assuming that the discharge in the tube ST is between the common anode and the main cathode K1, current flows also from the auxiliary anode A1 to the cathode K=1. The potential on the anode A1 falls sufiiciently for a discharge to be struck between the anode of the register tube and its cathode 1. At the same time resistors R11 and R21 form a potential divider and, with the component values given the terminal TT is not more than about 35 to 40 volts positive with respect to the conducting auxiliary electrode. The potential on the terminal TI acts as a bias applied to the cathodes 2, 3 and so on of the register tube through the resistor R12 to R219. The cathodes 2, 3 and so on are thus held at far too high a potential for a discharge current to flow to them from the anode of the register tube.

The anode currents in the two tubes can be set substantially independently by appropriate selection of the resistors RS and RR. The cathode current of the tube ST of course equals the sum of the anode currents of both tubes.

1 claim:

1. A multielectrode glow discharge tube comprising a common electrode, a plurality of main electrodes adjacent the common electrode, a plurality of guide electrodes intermediate the main electrodes for transfer of a glow discharge from main electrode to main electrode and a plurality of auxiliary electrodes each associated with a main electrode individual thereto and each disposed in that region between the associated main electrode and the common electrode which is occupied by a glow discharge struck between that main electrode and the common electrode.

2. A tube according to claim 1, wherein the effective surface area of each main electrode which has an associated auxiliary electrode is greater than the surface area of the guide electrodes.

3. A multielectrode glow discharge tube comprising a common electrode, a plurality of main electrodes adjacent the common electrode, a plurality of guide electrodes intermediate the main electrodes for transfer of a glow discharge from main electrode to main electrode and an auxiliary electrode associated with a main electrode and disposed in that region between the associated main electrode and the common electrode which is occupied by a glow discharge struck between that main electrode and the common electrode.

'4. A multielectrode glow discharge tube comprising a common electrode, a sequence of main electrodes adjacent the common electrode at a first spacing therefrom, a plurality of guide electrodes intermediate the main electrodes for transfer of a glow discharge from main electrode to main electrode, the guide electrodes being at a second spacing, less than the first spacing, from the common electrode, and a plurality of auxiliary electrodes intermediate the main electrodes respectively and the common electrode at the same, second spacing from the common electrode as the guide electrodes, each auxiliary electrode being on the direct line from a main electrode to the common electrode.

5. A multielectrode glow discharge tube comprising a common electrode, a sequence of main electrodes adjacent the common electrode at a first spacing therefrom, a plurality of guide electrodes intermediate the main electrodes for transfer of a glow discharge from main electrode to main electrode and also at the first spacing therefrom, and a plurality of auxiliary electrodes intermediate the main electrodes respectively and the common'electrode at a second spacing, less than the first spacing, from the common electrode each auxiliary electrode being on the direct line from a main electrode to the common electrode.

, 6. A .multielectrode glow discharge tube comprising a common electrode disc, a ring of main electrode Wires on a cylindrical surface coaxial with the disc, a ring of guide electrode wires intermediate and parallel to the main electrode wires for the transfer of a glow discharge from main electrode to main electrode, and a ring of auxiliary electrode wires having at least glow intercepting portions thereof intermediate the main electrode wires respectively and the main electrode disc and parallel to the main electrode wires.

7. A tube according to claim 6, wherein said auxiliary electrode wires are cranked, having glow intercepting portions on one cylindrical surface coaxial with the main '8 electrode disc, lead portions on -another coaxial cylindrical surface of lesser radius and radial portions interconnecting the glow intercepting and lead portions.

8. A tube according to claim 6, wherein the main electrode wires are thicker than the guide electrode and auxiliary electrode wires.

9. A multielectro-de glow discharge tube comprising a common electrode, a plurality of main electrodes adjacent the common electrode, a plurality of guide electrodes intermediate the main electrodes for transfer of a glow discharge from main electrode to main electrode and a plurality of auxiliary electrodes associated with the main electrodes respectively individual thereto and each disposed in that region between the associated main electrode and the common electrode which is occupied by a glow discharge struck between that main electrode and the common electrode.

.10. A circuit arrangement comprising a first multielectrode glow discharge tube and a register tube, the first said tube having a common anode, a plurality of main cathodes adjacent the anode, a plurality of guide electrodes intermediate the main cathodes for transfer of a glow discharge from main cathode to main cathode, a plurality of auxiliary anodes associated with the main cathodes respectively and each disposed between the associated main cathode and the common anode, the register tube having 'a plurality of cathodes connected to the auxiliary anodes respectively of the first said tube, the circuit further comprising a common terminal and a plurality of resistors connecting the auxiliary anodes respectively to the common terminal.

'11. A circuit arrangement according to claim 10, comprising means for maintaining the common terminal at a potential sufficiently high enough to prevent all cathodes of the register tube, other than that cathode connected to the auxiliary anode associated with the glow invested main cathode of the first said tube, from becoming invested with a glow.

References Cited in the file of this patent UNITED STATES PATENTS can-um..."- 

10. A CIRCUIT ARRANGEMENT COMPRISING A FIRST MULTIELECTRODE GLOW DISCHARGE TUBE AND A REGISTER TUBE, THE FIRST SAID TUBE HAVING A COMMON ANODE, A PLURALITY OF MAIN CATHODES ADJACENT THE ANODE, A PLURALITY OF GUIDE ELECTRODES INTERMEDIATE THE MAIN CATHODES FOR TRANSFER OF A GLOW DISCHARGE FROM MAIN CATHODE TO MAIN CATHODE, A PLURALITY OF AUXILIARY ANODES ASSOCIATED WITH THE MAIN CATHODES RESPECTIVELY AND EACH DISPOSED BETWEEN THE ASSOCIATED MAIN CATHODE AND THE COMMON ANODE, THE REGISTER TUBE HAVING A PLURALITY OF CATHODES CONNECTED TO THE AUXILIARY ANODES RESPECTIVELY OF THE FIRST SAID TUBE, THE CIRCUIT FURTHER COMPRISING A COMMON TERMINAL AND A PLURALITY OF RESISTORS CONNECTING THE AUXILIARY ANODES RESPECTIVELY TO THE COMMON TERMINAL 